a question of short interdigital filter's bandwidth

i study filter presently. i am design a short interdigital filter,2G~4G frequency range .someone told me that my filter's bandwidth((f1-f2)/f0) is too large to design the short interdigital filter.
i want to know how much short interdigital filter'bandwidth is.and open interdigital filter'bandwidth.and tapped interdigital filter'bandwidth.
thanks.